Five Revelations From the U.S. Embassy’s Beijing Pollution Data Dump

Beijing residents have often wondered whether the city’s air pollution is getting better or worse.

Although the U.S. Embassy in Beijing and the Chinese government both publish air-quality readings every hour, limited historical data is publicly available. This partly changed last month when the U.S. State Department posted online a treasure trove of data showing hourly readings taken since 2008 at an air-monitoring station at its Beijing embassy.

The State Department cautions that the data isn’t scientific or validated (the readings come from one isolated monitoring station in one part of the city). The information is “for the express purpose of providing U.S. citizens living and traveling abroad [with] actionable health information related to air pollution,” it said in a statement.

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Still, China Real Time crunched some numbers and came up with five takeaways:

1. Beijing’s PM2.5 levels aren’t getting worse.

But they aren’t getting much better either. Beijing’s hourly PM2.5 levels have averaged about 100 micrograms per cubic meter each year since 2008. That’s more than eight times the U.S. Environmental Protection Agency’s annual standard of 12 micrograms per cubic meter. Chronic exposure to particles in the air—especially at extremely high concentrations—increases risks for cardiovascular and respiratory diseases, as well as lung cancer, according to the World Health Organization.

2. Fireworks are bad. Really bad.

Predictably, some of Beijing’s worst stretches of air pollution occur in the hours before and after midnight over the Lunar New Year holiday. This is likely due to the sheer amount of fireworks being set off within city limits. Because of fireworks celebrations during the Lunar New Year holiday, Beijing’s most-polluted hour since 2008 was between 11 p.m. and midnight on Jan. 23, 2012. PM2.5 levels rose to a record 994 micrograms per cubic meter, a milestone that’s just waiting to be broken.

3. However bad it gets, it likely won’t be as bad as Jan. 12, 2013.

Beijing’s most-polluted day since 2008 came during a period expatriates dubbed “airpocalypse.” The average 24-hour concentration of PM2.5 rose to 569 micrograms per cubic meter. That’s more than 16 times the EPA’s 24-hour standard of 35 micrograms per cubic meter.

4. The air was better during the Olympics—but still ‘unhealthy.’

During the 2008 Beijing Olympics, which ran from Aug. 8-24, hourly concentrations of PM2.5 averaged 54 micrograms per cubic meter. Although most Beijing residents would be happy with these levels, the EPA says an index of between 35.5 and 55.4 is still “unhealthy for sensitive groups.”

5. We should all look forward to the annual National People’s Congress.

With the exception of 2013, the annual meeting of China’s legislature, which lasts at least nine days, traditionally ushers in a stretch of cleaner air in Beijing, with PM2.5 readings averaging 83 micrograms per cubic meter. That’s below the annual hourly average of 100 micrograms per cubic meter. The National People’s Congress in 2013 bucked the trend, with hourly levels averaging 164 micrograms per cubic meter.

About China Real Time Report

China Real Time Report is a vital resource for an expanding global community trying to keep up with a country changing minute by minute. The site offers quick insight and sharp analysis from the wide network of Dow Jones reporters across Greater China, including Dow Jones Newswires’ specialists and The Wall Street Journal’s award-winning team. It also draws on the insights of commentators close to the hot topic of the day in law, policy, economics and culture. Its editors can be reached at chinarealtime@wsj.com.